Somewhere between 7,500-4,000 years ago, a meteorite fragmented over Estonia's Saaremaa island. The meteorite hit with a force comparable to Hiroshima and left nine impact craters, including the 110-meter Kaali crater. Locals worshiped this hole as holy.

Several kilometers above the earth's surface, the meteorite broke into pieces from the pressure and heat of the atmosphere. The resulting chunks collided into Saaremaa with the force of a small nuclear bomb, wreaking havoc on the landscape and possibly claiming numerous victims.

The explosion left nine total craters, now known as the Kaali Meteorite Crater Field. Some of these craters are quite small: one measures only twelve meters across and one meter deep. But the most interesting of the group is the largest crater, a gently sloping bowl filled with stagnant, murky water.

Simply known as Kaali crater, the largest crater (which measures 110 meters across) is believed to have been a sacred site for many centuries, in part due to its cosmic origin. Surrounding Kaali crater are the remains of an immense stone wall from the Late Bronze Age, stronger than any similar structures in the region and providing clues to the crater's use by ancient peoples.

1500-to-2000-year-old animal remains found around Kaali Lake have led archaeologists to believe that the crater was the site of ritualistic sacrifices. You can read more about the geology and formation of the Kaali crater at Geologos.